Walt Patterson

Margaret Gowing’s masterly official history of postwar nuclear activities in Britain, Independence and Deterrence, describes disputes among the nuclear physicists at the Atomic Energy Research Establishment at Harwell:1

The only point on which there was general agreement… was on the long term future on the ultimate and overriding importance of breeder reactors, which would produce more secondary fuel than the primary fuel they consumed.

The reason for this island of unanimity amid the prevailing conflict of views was straightforward. In the late 1940s and early 1950s uranium was scarce and expensive; moreover its supply was politically acutely sensitive, because of the weapons implications.

In consequence, as Harwell director Sir John Cockcroft explained:

… we have to develop a new type of atomic pile (reactor) known as the ‘breeder pile’ because it breeds secondary fuel (plutonium) as fast or faster than it burns the primary fuel uranium-235 ….These piles present difficult technical problems, and may take a considerable time to develop into reliable power units. Their operation also involve difficult chemical engineering operations in the separation of the secondary fuel from the primary fuel.

By 1953, nuclear engineers at Risley, after working for some two years with their Harwell colleagues on the design of a fullscale fast breeder power station, concluded:

Edited, abridged and updated from Going Critical: An Unofficial History of British Nuclear Power, Walter C. Patterson, Paladin, 1985.

At first sight this fast reactor scheme appears unrealistic. On closer examination it appears fantastic. It might well be argued that it could never become a serious engineering proposition.

Nevertheless, in March 1955, construction work started on an experimental fast breeder power station at the new Atomic Energy Authority’s (AEA) Dounreay Experimental Reactor Establishment, on the north coast of Scotland. This remote location was chosen precisely for its remoteness, because of major questions about the possible behaviour and misbehaviour of a reactor whose core contained an unprecedented concentration of fissile material.

By the third AEA annual report, in mid-1957, the Dounreay Fast Reactor (DFR) was "expected to start operation in 1958". From 8 October 1957, however, the AEA was preoccupied with the aftermath of the Windscale fire, in which one of its graphite-moderated plutonium production reactors had burned and dispersed a large amount of radioactivity. The DFR did not actually go critical until November 1959. The 1960 annual report remarked, "A prototype power producing reactor may be built for operation about the year 1967, the development of which will enable a commercial power station to be specified."

The design output of the DFR was to be 60 megawatts of heat (MWt), or 14 megawatts of electricity (MWe). Successive AEA annual reports stressed that the DFR was "experimental," "intended to develop the technology of fast reactors generally." It fulfilled this role admirably, in that it succumbed to a fascinating variety of novel engineering difficulties, particularly those arising from the use of molten-sodium-potassium alloy as the cooling fluid. By mid-1961 its highest output had been 1.5 MWt. By mid-December the reactor had been run up to 11 MWt, at which point it was shut down to have its fuel core replaced with one of improved design. While thus busy with the DFR, the AEA in 1961-62 was also completing a design study for a 500 megawatt (MW) fast breeder power station. The next step in the program would be to try out the concepts on an intermediate scale, on what would be known as the Prototype Fast Reactor (PFR). The DFR reached an output of 30 MWt, half its intended design output, on 7 August 1962, and remained at this level for the rest of the year. In October it supplied electricity to the national grid for the first time.

The Select Committee on Nationalized Industries, in its May 1963 report on the electricity supply industry, noted that "the development by the Atomic Energy Authority of a fast breeder reactor at Dounreay… remains a long term project. The Authority hopes that a prototype will be operating by 1969 or 1970; and the first civil station would not be working before 1975." The 1963-64 annual report of the AEA declared that "Consortia design engineers are engaged on a design study of a 1000 MWe power producing fast reactor." At the time, the largest thermal reactors contemplated for construction were 660 MWe. In July 1963 the DFR at last attained its full design output of 60 MWt, or 14 MWe, and operated at this level for most of the ensuing year.

In 1964-65, the AEA completed two design studies for fast breeders. The first was for the proposed PFR. It was to have an output of 600 MWt or 250 MWe; but it was designed to use components suitable for a full scale commercial fast breeder power station. By August 1965 AEA staff were already preparing detailed designs and specifications for major plant and civil engineering contracts for PFR. This was well before the official go-ahead for PFR, which did not come until 9 February 1966.